1. Field of the Invention
The present invention relates to a buckle device adapted for use in seatbelt system for protecting an occupant in an emergency situation of such a vehicle as an automobile or an airplane and more particularly to a buckle device improved in locking portion between a lock lever and a tongue plate.
2. Description of the Prior Art
As is well known, the buckle device is such constructed that a tongue plate secured to one end of an occupant-restraining webbing is inserted into a buckle body and a lock lever disposed in the buckle body is latched to an opening portion of the tongue plate to prevent the tongue plate from being pulled out, whereby an occupant is placed in his webbing-fastening situation.
Also, in case that the occupant releases the webbing-fastening situation, he pushes down a release button mounted on the buckle body to cause the lock lever to separate from the opening portion of the tongue plate, thereby to pull the tongue plate out of the buckle body.
FIGS. 1 and 2 are a plan view and a sectional view showing a locking portion of a conventional buckle device.
A buckle body 10 is provided therein with a lock lever 12, and a pawl 14 formed on the lock lever 12 is caught in an opening portion 18 of a tongue plate 16 inserted in the buckle body 10. In this case, the pawl 14 usually contacts with the opening portion 18 approximately at their center portions 19, as shown in FIG. 1, but the contact portions of the pawl 14 and the opening portion 18 are moved in accordance with variations of load acting upon the webbing. That is to say, in such a condition that the tongue plate 16 is locked into the buckle body 10 a clearance exists between the inside of the buckle body 10 and each of both side edges of the tongue plate 16, and in such a condition the tongue plate 16 is slightly rotatable centering around the center portions 19 in directions of the width of the buckle body 10. Therefore, the contact portions of the pawl 14 and the opening portion 18 are moved rotatably centering around the center portions 19 due to changes of attitude of the occupant fastened by the webbing or the like.
Accordingly, the pawl 14 and the opening portion 18 of the tongue plate 16 are caused to contact with, or rub against, each other approximately all over their locking faces in accordance with increase in number of use of the buckle device, and the locking faces are made rough approximately in their whole surfaces, whereby most of the respective locking faces is decreased in smoothness and the friction between both the locking faces is increased approximately all over the locking faces. As a result, when a large load acts upon the webbing, for example, when the centre portions 19 are deformed or crushed in such an emergency situation of the vehicle as a collision and the contact portions of the opening portion 18 and the pawl 14 are enlarged, portions of the opening portion 18 and the pawl 14 newly caused to contact with each other in the emergency situation have already been made rough, i.e., they have already been increased in frictional force therebetween, as set forth above, and, therefore, in order to release the tongue plate 16 from the pawl 14 it is required that a release button (not shown) mounted on the buckle body 10 is operated with a large force, or power.